Manufacture of steel.



UNITED STATES PATENT OFFICE.

FRANK D. CARNEY AND LEWIS IB. LINDEMUTH, OF BETIEILEHEM, PENNSYLVANIA.

MANUFACTURE OF STEEL.

No Drawing.

To all whom it may concern:

Be it known that we, FRANK D. OARNEY and LEWIS B. LINDEMUTH, bot-h citizens of the United States-of America, and residents of Bethlehem, N orthampton county, Pennsylvania, have invented certain new and useful Improvements in the Manufacture of Steel; and we do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it app ertains to make and use the same.

This invention relates to the manufacture of steel by the duplex p'rocess, namely, where the pig iron is first treated in a Bessemer converter, and then treated under basic conditions in a basic lined open hearth, or equivalent, furnace for further purification. The steel is then run into ingot molds, and the ingots suitably treated and manufactured into commercial rolled shapes.

There has been much difiiculty in producinlgthese commercial shapes, as rails and ot r rolled shapes, free from such flaws as seams or small cracks when made of duplex steel, and we have found that often the cause of these flaws may be traced back to conditions occurring in the open hearth furnace, in even the most approved open-hearth practice when treating bessemerized iron.

The object of this improvement in the practice is to prevent the breaking and crackin of the ingot surfaces during rolling, an to produce a finished product more free from the defects known as seams? Of course, the outer surface of the ingot may be removed, but this entails, in addition to the loss of metal that has no value beyond that of scrap metal, also the cost of labor, and the expense due to loss of heat.

We have found that it is most desirable to overcome these .defects by giving the metal more perfect casting properties or characteristics, so that these imperfections are not liable to occur from the quality of the steel, and we have done this with marked success.

We have discovered that a large part of the surface defects in the finished, metal may be prevented by carrying during the whole of the refinin process a slag in the basic open hearth urnace with a suflicient content of manganese oxid, that manganese may be reduced from the slag and enter the metal in the 0 en hearth furnace, so that such metal wil at all timesduring the re:

Specification of Letters I'atent. Patented Apr. 17, 1917.

Application filed November 20, 1916. Serial No. 182,399.

fining process in the basic open hearth furnace, contain in the neighborhood of .18% man anese, and preferably 20% or over. To 0 tain this condition during the refining process-the slag in the basic open .hearth furnace must (ontain not less than 10.0% manganese oxid.

It is known that in the duplex process manganese in t1 1e pig iron charged into the Bessemer converter, is eliminated early in the blow, except where such iron contains from three to fir e per cent. manganese, which is not a condition existing in this country, nor any place, except, per aps, Sweden and orway.

The charge tien t0 the open hearth furnace, which is entirely blown metal from a Bessemer converter, excepting ore, alloy and other necessary furnace additions, will contain from a trace to 05% manganese. Such a charge will nct produce a steel of the best rolling qualities, for, as we have found, both the slag and bath of metal have had their manganese content depleted. Such a con dition will allow iron oxid to be formed from the bath of metal, and to enter the bath, giving the steel an appreciable per centage of this oxid, which in turn destroys to a certain extent the good rolling qualities of ingots cast fr am it.

It is known, and has always been customary, in the manufacture of steel by any process, to add manganese at the finish of .the process eith1 :r in the furnace or ladle or both, to give ti 1e steel the pro er rolling qualities. This manganese is a ded, sometimes in conjunction with ferro-silicon, aluminum, ferro titanium, or other deoxidizing elements, to deoxidize the metal after it has been refined.

By our method of making a slag in u the basic open Iiearth furnace r refining bessemerized iro a, the slag is saturated with manganese oxid to an extent that manganese reduces from the sla and passes into the metalof the bath, and oxidation of iron in the bath, or abs 1 tion of oxid by the bath, is prevented b tlie residual man anese in the bath whic oxygen than iro 1. When the charge in the open hearth fur aaee is read to be tapped, the residual manganese wil be 0.18% to 0.30% with a s1: g of 10% manganese oxid,

or higher, if a ,greater percentage of man-- has a. greater a nity for ganiferous mate rials have been added and the slag volume: remainsconstant,

' appreciably more free from To obtain such a percentage of residual manganese in the open hearth metal we have found that it is necessary to form a slag that will analyze at least manganese oxid.

In order to obtain such a sla and such an open hearth metal, we intro uce into the open hearth furnaceeither before or with the charge, -or during the refining stage,

manganese materials, such as ferro-manganese or manganese ore, preferably the latter, in sufiicient quantity to-produce a sla having the manganese content above-mentioned; a part of the manganese will ,then be reduced by the usual reactions from the slag and enter themetal bath below it in a quantity sufficient to prevent a great part of the oxidation of iron in the bath provided the manganese content of the slag is at least 10% manganese oxid. The surfaces of the ingots produced by our process are more ficient manganese bearing material to produce a slag under basic conditions whose manganese content is sufiicientl great to permit a reduction of a portion 0 said manganese content and cause its entranceinto and its retention in the metal of the bath beneath it.

2. The method of making duplex steel, which comprises charging bessemerized metal into a basic open hearth furnace, then'charging sufiicient manganese bearing material to produce a slag under basic conditions whose manganese content is sufliciently great to cause a portion of its manganese to enter the metal beneath it, and causing the metal of the bath to contain at least 0.15% manganese during the entire refining operation.

3. The method of making duplex steel, which comprises charging bessemerized metal, into a basic open hearth furnace with sufficient manganese material to produce a slag under basic conditions having a content of manganese oxid of ten per cent. or over.

4. The method of making duplex steel, which comprises charging bessemerized metal into a basic open hearth furnace with manganese ore suflicient to produce a slag containing about ten per cent. manganese oxid under basic conditions existing 1n, the fur nace.

In testimony that we claim the foregoing as our invention, we. have signed ournames in presence of two subscribing witnesses.

Witnesses:

E. D. HAEHNLE, R. M. BIRK. 

